In Pedersen U.S. Pat. No. 3,883,912, assigned to the assignee of the present application, there is disclosed a single anchor leg mooring system in which converging, vertically and horizontally swiveling submerged hose arms terminate at a support float counterbalanced by a depending weight. This arrangement will permit vertical angular movements which will relieve vertical bending strains in the cargo hoses due to dynamic and static forces acting on the hose, and at the same time resist excessive deviations from the desired optimum angle of inclination of the hose arm. Excessive variations from the optimum angle of inclination will significantly reduce the torque effect of the hose arm.
The ability of the arrangement disclosed in U.S. Pat. No. 3,883,912 to resist vertical movements of the hose arm is proportional to the physical dimensions of the buoyancy tank and counterweight structure. For large cargo swivels with relatively high torque resistance, the effective embodiment of this arrangement may require very large physical dimensions in order to provide adequate resistance against being pulled upward to the extent that horizontal torque capacity is reduced to a value which is insufficient to overcome the actual torque resistance of the cargo swivel. Such large dimensions, particularly with respect to height requirements, cannot always be accommodated, and the arrangement is found to be impractical at locations where the vertical clearance between the tanker keel and the sea bottom limits the space available for such hose arm arrangements.